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Human's "personality glasses" - Why we form impressions of individuals. New insights into a uniquely human ability

The ability to quickly form impressions of other individuals'
"personality" seems to be a uniquely human ability. A 3-year
cross-species study of 104 crab-eating macaques and 99 human observers of these
monkeys further explored this fascinating human ability. The study illuminated
the ways in which judgements of individuals are influenced by beliefs about age,
status and sex differences that are rooted in our everyday knowledge and that
tend to be stereotypical. These intuitive beliefs are like glasses through which
we form impressions of the "personality" of individuals. These beliefs
even affect how we judge individuals of other species! The study unravels common
mistakes that we make when forming impressions of individuals. But despite
widespread inaccuracies and mistakes, the ability to quickly form impressions of
strangers could have been of enormous importance in human evolution: It enabled
our ancestors to trade with unknown individuals of foreign cultures, and it was
also an essential prerequisite for the domestication of animals. An exciting
study about humans and monkeys from different continents. ´

Information about who is doing what with whom plays an essential role in our everyday lives. By communicating such information, we exchange experiences that we have
had with particular individuals as well as our ideas and opinions about these individuals. Within our sociocultural communities, we develop shared beliefs and values about individuals and their peculiarities as well as a shared language
for communicating this information.

Our everyday language therefore contains numerous words that we can use to efficiently and quickly communicate complex information about individuals. We use the
small piece of information that somebody is "friendly" to draw conclusions about an individual
whom we have not yet met and we align our actions accordingly. This is possible because our everyday knowledge contains a differentiated system of social categories. This system is partially based on our own experiences, but in particular on our everyday language, i.e., on the experiences and beliefs of previous generations. Therefore, all individuals of our cultural and language community share this knowledge system in similar ways.

We intuitively use this knowledge system when we encounter foreign individuals to mentally categorise these individuals with regard to their "personality" and to form impressions about how they may behave towards us. But even if first impressions do not always prove to be fully accurate, they provide a sense of security in dealing with unknown individuals and offer clues
by which we adjust our behaviours also proactively.

The ability to deal peacefully with foreign or even anonymous individuals is
so common in our daily lives that, at first glance, it does not seem to be any
special. But it may be uniquely human, at least when only mammalian species are
considered. Even our closest living relatives, the nonhuman primates, show
tremendous difficulties in dealing peacefully with unknown conspecifics. We are
able to sit tight and calmly next to strangers, such as in public transport.

But
for many other species, encounters with strangers are extraordinarily stressful
and often involve aggressive conflicts, some even with fatal outcomes.
"Especially in the great apes who are often so amazingly similar to us with
regard to many social and cognitive abilities, is is often disturbing to see how
stressful encounters with strangers are for these individuals and how these
encounters sometimes escalate into violence", says Jana Uher, the director
of the study. Why is that so?

Jana Uher suggests that this is not only a consequence of other species' greater
territoriality and their general lack of abstract language ability in and of
itself. Instead, stressful encounters may result from a lack of the ability to
develop mental categories of individuals that can be used to assess unknown
individuals with regard to their "personality". The researcher
explains: "Without a basic knowledge of the ways in which individuals
differ from one another in their behaviours, that is, without
"personality" categories that are useful for differentiating between
individuals, one cannot mentally categorise an unknown individual and therefore
cannot deduce assumptions about how it may behave next.

Thus, every encounter
with strangers is characterised by high uncertainty and one can learn only
stepwise from interactions with a stranger how he or she may tend to
behave." In view of the stressful encounters with unknown conspecifics,
Jana Uher assumes that not even the great apes are able to develop mental
categories of individuals and to use these categories to form impressions of
others. "This may explain why, for the individuals of many nonhuman
species, such encounters are often difficult, and why, in zoological
institutions, introductions of new individuals are often so stressful",
Jana Uher says.

The researcher emphasises, however, that individuals of many nonhuman species are able to learn over some time how particular individuals in their social environment tend to behave; otherwise, individualised relationships could not be found in other species as well, in particular in primates.
But the ability to develop general categories about individual differences from peculiarities of single individuals and to use using these categories in social interactions seems to be a uniquely human ability.

In our everyday lives, we use this ability so
intuitively that, at a first glance, it does not seem to be any special. Rather,
its uniqueness could be revealed only through comparisons with other species. To further explore this ability, Jana Uher and her research colleagues from the ethology station of the Dutch
Utrecht University investigated how humans form "personality" impressions of individuals of other species.

Our ability to recognise individual differences in the behaviour of nonhuman species was an essential prerequisite for the domestication of animals. For a long time, it was assumed that our ancestors had domesticated animals based on selective breeding for bodily features. But groundbreaking breeding experiments with farm foxes in Russia have impressively shown that selective breeding for specific individual behaviours-less fear of and aggression towards
humans - results within only 30 generations in a host of physical changes
through which today's domesticated animals differ markedly from their wild relatives.

Stone-age fossils that resemble today's dogs more than wolves suggest that, as early as some 30,000 years ago, humans had to have already been able to mentally develop "personality"
categories that are useful for differentiating individuals of other species as well.

Domesticated animals have been bred for those particular behavioural properties that we as humans can easily perceive and for which we have developed "personality"
categories in our everyday language. Therefore, Jana Uher and her research team explored how humans develop "personality"
impressions of individuals of a nonhuman species with which the
observers were previously inexperienced - crab-eating macaques from Southeast-Asia.

In the ethology station's colony that is has been studied for their social behaviours for decades already, 91 students of behavioural biology first learned about this particular monkey species and about scientific methods of behavioural observation. Then, the students worked in pairs; each pair intensely observed 5 monkeys over 5 days and systematically recorded their behaviours. Thereafter, they assessed their 5 monkey individuals with two "personality" questionnaires. In addition, 8 researchers from the ethology
station assessed the monkey individuals many of which they had known for several years.

The results were intriguing. "I had assumed that observations of just 5 individuals of a species with which one was previously not familiar
would not be sufficient to form impressions of their individual peculiarities that
would be comparable to the impressions that other observers formed of the monkeys several weeks later and, importantly, that
would be comparable to the experts' impressions.

But astonishingly, we found hardly any differences.", says Jana Uher. Moreover, to get to know individuals, 5 days
is only a very brief amount of time, despite the use of systematic scientific observations. "Without the robust findings that we obtained from 6 study waves over 3 years, I would have had doubts
about whether this could be possible at all", she says. This shows how quickly we form impressions of individuals of other species and how similar the impressions are that we form of them. But how accurate are they?

To find this out, the researchers used a novel paradigm to categorise individual differences. In contrast to previous studies, these new approaches are not based on human's everyday language, but instead on the behavioural repertoire of those individuals whose "personality" is under
study; in this case crab-eating macaques. "These new approaches enable us to clearly differentiate and compare how individuals behave
with what observers think about how individuals behave. This is not possible with the previous methods used in
"personality" psychology that are rooted in everyday language", explains Jana Uher. She has developed the new paradigm and has already applied it successfully in studies on individual behaviours of capuchin monkeys and great apes and on human observers' impressions of these individuals' "personality".

The results were amazing. The observers judged younger crab-eating macaques
as more curious and impulsive than older ones, high-ranking monkeys as more impulsive than low-ranking ones, and females
as more clean than males. But none of these age, status and sex differences were found in the monkeys' behaviours. Moreover, younger monkeys behaved more anxiously than older ones and males more anxiously than females, but this was not reflected in the observers' "personality" judgements. The results are consistent with stereotypical beliefs about human individuals. This shows that such beliefs can also bias judgements about monkey individuals in anthropomorphic ways.

As human "personality" differences have been studied almost exclusively with questionnaires so far, it is still unknown in what ways "personality"
judgements of human individuals are biased by stereotypical beliefs, such as about persons of different age, sex/gender or social and ethnic background. Judgements reflect what people think about
and how they describe themselves and other humans or even individuals of other species
- but judgements cannot reflect how the judged individuals actually behave. Only comparisons with the individuals' behaviours can show to what extent we form accurate impressions of individuals through our "personality glasses" and in
what ways we jump too quickly to using our everyday knowledge and potential stereotypical or anthropomorphic beliefs.